Time resolved measurements of melting and solidification in Si using third harmonic generation of light

Time resolved measurements of melting and solidification on (001) Si using third harmonic generation (THG) were performed with subpicosecond time resolution. Following 120 fs laser pulses at fluences above the melt threshold, the circularly polarized THG signal decreases by over three orders of magnitude. It regains its original intensity on solidification after approximate to 2 ns. The authors show that the THG signal is sensitive to specimen temperature, decreasing by a factor of approximate to 5 between 298 K and the melting temperature. The work demonstrates that complete thermal and phase histories can be obtained during ultrafast laser heating using single-shot THG experiments. (c) 2007 American Institute of Physics.